To ensure proper nutritional support for newborn infants, many doctors and hospitals recommend the use of liquid pediatric nutritional products. Pediatric nutritional products are utilized when breast feeding is not possible for either medical and/or social reasons. Furthermore, even in cases where breast feeding is possible, some mothers prefer the convenience afforded by the use of pediatric nutritional products.
In response to the need for pediatric nutritional products soy and milk-based liquid foods have been developed for bottle feeding in conjunction with a rubber or latex nipple. Since the containers for these products should provide a twelve to eighteen month shelf life, a hermetic seal must be provided across the top of the container. A hermetic seal is one which when in place is impervious to microbiological intrusion and external influence. Presently the industry provides a hermetic seal through the use of a glass container, to which is secured by vacuum closure a stamped steel cap having a pre cut rubber, or vinyl plasticol gasket. This vacuum closure of the container is then subjected to temperatures above the ambient air temperature, and more specifically to retort conditions, whereby the hermetic seal must survive sterilization of the nutritional product and the container. Since the glass container and the stamped steel cap expand a similar amount and since a vacuum is present within the container, the hermetic seal is maintained during the sterilization process.
Due to concerns about material cost, container weight, and breakage, suppliers of nutritional products have sought to manufacture the nutritional product container from a plastic substance, such as polypropylene, which is relatively clear, optically and cost effective as compared to glass. The problem arises in attempting to provide a cap for a plastic container which maintains a hermetic seal.
Since it is difficult to maintain a vacuum in a plastic container and conventional metal caps and plastics expand by a dissimilar amount, conventional metal caps can not maintain a hermetic seal for plastic containers when subjected to retort conditions. Furthermore, the application of heat under retort conditions causes polymer relaxation or shrinkage, especially in the upper neck portion of the container. Injection or extrusion molded bottles are formed by stretching the polymer molecules while the heat of sterilization causes those molecules to relax and actually shrinks the diameter of the neck. This shrinkage causes problems in maintaining a conventional metal cap on a plastic bottle. This shrinkage also prevents the use of a conventional plastic cap on a plastic bottle.
One solution to these problems would be to apply a substantial amount of torque when initially capping the bottle, however the amount of torque necessary to maintain a conventional cap in place is so high that a person would not be able to easily twist off the cap following retort. Another possible solution would be to fabricate a bottle from a plastic which does not shrink at retort temperatures and can maintain an internal vacuum without distortion. However, the cost of providing such a bottle is prohibitive.
Another possible approach to the providing of a hermetic seal to a plastic container would be to utilize a barrier membrane, such as aluminum foil, such that the integrity of the seal is independent of the closure. This primary membrane seal would be protected from accidental or premature puncture by an overcap of a conventional design. One type of foil seal is the type which is peelable.
However, in dealing with nutritional products subject to spoilage, peelable seals are not optimal for maintaining confidence that the product has not been tampered with, or for ensuring against spoilage.
A heat fused foil seal, which imparts a permanent seal, is desirable. However, the use of a heat-fused foil membrane necessitates that the outer cap be removed, followed by the piercing of the membrane seal with of a microbial laden device, such as scissors or a fingernail, thereby contaminating the product with bacteria.
It is thus apparent that a need exists for an improved closure for a pre filled, membrane sealed nutritional product container which provides system seal integrity, as well as permitting the opening of the nutritional products container in a single action motion.